Shrimp biology and culture

1. SHRIMP GROW-OUT CULTURE
TECHNIQUES IN THE PHILIPPINES
Apolinario Gicos
Bureau of Fisheries and Aquatic Resources
Department of Agriculture
Quezon City, Philippines
The major commercial shrimp species in the Philippines belong to the
genus Penaeus and Metapenaeus. The important penaeid shrimps are: P.
monodon (giant tiger shrimp or sugpo); P. japonicus and P. semisulcatus (tiger
shrimp and bulik or sugpo); and P. merguiensis and P. indicus (white shrimp and
Indian white shrimp or putian). The giant tiger shrimp is the major species
cultured in ponds while the others are incidental crops.
There are 210,000 ha of potential and existing brackishwater ponds in the
Philippines (Fig. 1). Because most of these are underdeveloped, present
technologies are aimed at improving production or encouraging the develop-
ment of new areas.
Brackishwater fishfarming in the country is primarily centered on milkfish
(Chanos chanos) (Table 1). Shrimp used to be merely an incidental crop when
postlarvae from the wild enter the milkfish ponds. In the last decade, many
traditional milkfish growers recognize the market of shrimps, primarily the
giant tiger shrimp. Polyculture of milkfish and shrimp was practiced, and the
fishfarmers shifted to shrimp monoculture when price of shrimp in the interna-
tional market went up.
In the mid-70s, SEAFDEC/AQD developed and extended its shrimp
hatchery technology, and hatcheries proliferated throughout the country. Seed
supply became abundant, encouraging more people to invest in grow-out
culture. However, production remained low and inconsistent since the grow-
out technology remains largely an art.
When Taiwanese grow-out technology was introduced in the country
and research in shrimp was intensified in the Department of Agriculture,
University of the Philippines, and SEAFDEC/AQD, new coastal areas were de-
veloped particularly in Negros Island where vast tracts of sugarland and rice
land were converted to shrimp ponds. Milkfish ponds were also renovated for
shrimp culture.
There are four shrimp culture levels in the country, namely: traditional,
extensive, semi-intensive, and intensive which vary mainly in pond design,
stocking density, feeds and feeding, and water management (Table 2). Only the
semi-intensive and intensive culture systems are discussed.
Proceedings of the Aquaculture Workshop for SEAFDEC/AQD Training Alumni; 8-11 September
1992; Iloilo, Philippines. SEAFDEC Aquaculture Department, Iloilo, Philippines. 1993. 173 pp.

2. Fig. 1. The Philippines: mangrove areas fishpond areas (•), and fishing
grounds. The eight provinces with the largest fishpond areas are indicated (Ps, Pangasi-
nan; Pm, Pampanga; B, Bulacan; Q, Quezon; C, Capiz; I, Iloilo; N, Negros Occidental; and
Z, Zamboanga del Sur) (Camacho and Bagarinao 1986).
36 Country Report: Philippines

3. Table 1. Brackishwater fishponds in operation
Region
Total
area
(ha)
Production (M t)*
Region
Total
area
(ha)
Bangus Sugpo Others** Total
NCR 703 503 56 85 644
I 16,658 16,955 3,765 5,806 26,566
II 1,469 680 19 244 943
III 53,465 49,477 12,058 11,717 73,252
IV 23,281 9,062 8,035 1,973 19,070
V 11,028 3,961 1,276 722 5,959
VI 59,074 64,959 15,699 4,143 84,801
VII 7,110 6,771 371 - 7,142
VIII 5,977 2,349 450 112 2,911
IX-A 1,540 1,293 20 53 1,366
IX-B 14,861 12,961 348 1,902 15,211
X 4,326 2,910 156 43 3,109
XI 7,248 6,012 603 1,964 8,579
XII 3,940 3,264 683 80 4,027
TOTAL 210,680 181,197 43,539 28,844 253,580
*Average national yield, 1.2036 Mt/ha/yr. **Tilapia, white shrimp, mudcrab,
others. NCR, national capital region.
Table 2. Comparative features of various technology levels of shrimp culture
Traditional Extensive Semi-intensive Intensive
1. Stocking
density
(pc/m2)
0.5-1.5 3.5 6.15 10 and above
2. Maximum
pond size (ha)
30 1.5 1.5 0.70
3. Minimum
water depth (m) 1.0 1.0 1.1 1.2
4.Aerators (/ha) None None 4-8 units
at 1 hp
4-8 units
at 1 hp
5. Feeds Fresh diet Commercial;
fresh diets
Commercial
feeds
Commercial
feeds
6. Water
supply
Tidal;
brackish-
water
Tidal;
brackish-
water
Pumping;
fresh-, sea-
brackish-
water; river
Pumping;
fresh-, sea-
water
7. Production
(Mt/ha/yr)
0.2 - 0.8 0.8 - 3.0 3.0 - 7.0 7.0 - 10.0
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Shrimp Grow-out Culture

4. Semi-intensive and intensive culture
Pond preparation. The pond bottom is sun-dried for 15 days or until the
pond bottom cracks and the surface turns whitish. The sluice gates are sealed
to control water level and to prevent entry of unwanted organisms. Dried ooze
is removed from the pond bottom by scrapping.
Ponds are plowed to further dry the pond bottom. Then, 1 t/ha of
hydrated lime is applied to obtain a soil pH of 7-7.5. Note that only 50% of the
required lime is initially applied, the remaining 50% after the second plowing.
The second plowing is made towards the gate where the bottom is more
depressed and unwanted species hide. The remaining 50% of the lime required
is applied with 21-0-0 to kill crabs and other crustaceans. Teaseed powder is
also applied for the same purpose two days before the pond is filled with water.
A water depth of 1 m is maintained. Dikes and gates are checked for leaks
and these are immediately repaired. Salinity of incoming pond water is prefera-
bly the same as in the source of fry. Floating debris and filamentous algae are
removed.
The appropriate number of paddle wheels is installed and positioned
parallel to the dikes for 1-ha or bigger ponds or oblique to the dikes for smaller
ponds. The number of paddle wheels installed varies with days of culture
(DOC), expected survival, and average body weight (ABW):
• if survival is < 8 0 % and A B W is <35 g
DOC No. of units
1 - 9 0 4
91 to harvest 6
• if survival is > 8 0 % and A B W is > 3 5 g
DOC No. of units
1 - 75 4
76 - 120 6
121 to harvest 8
Sampling of stock. Regular sampling is necessary to monitor growth and
survival, indices useful in adjusting the amount of feed given to stock. Sampling
is scheduled every 15 days preferably early in the morning or late afternoon. The
number of shrimps in the feeding trays is an adequate estimate when shrimps
are still small but cast net must be used for bigger shrimps. Different parts of
the ponds must also be sampled.
Water management. Water quality should be frequently monitored.
Change of pond water is usually adequate to maintain good water quality aside
from helping introduce new food organisms and stimulating the molting of
shrimps. If pond water remains stagnant for long, organic wastes may rapidly
38 Country Report: Philippines

5. decompose, and depletion of oxygen may affect shrimp growth.
Tidal exchange of pond water is normally practiced in traditional shrimp
farms. One half of the water is drained during low tide and replenished during
rising tide, the exchange done within 5 to 7 days of the spring tide. Refertiliza-
tion takes place after the last day of water replenishment.
Water pumps are used in semi-intensive and intensive cultures. For semi-
intensive culture, the pump is used only during neap tide because tidal water
can facilitate exchange during spring tide. About 50% of pond water is changed.
For intensive culture, frequent changes are essential to reduce decomposing
food and to maintain optimal oxygen level. One-third of pond water can be
changed by adopting a flow-through system.
Salinity
The ideal salinity for P. monodon is 15-25 ppt although it can tolerate a
much wider range. A refractometer is used to determine salinity before, during,
and after every water change.
Dissolved oxygen
The ideal DO level for shrimp is 4-8.5 ppm. This is maintained through
water replenishment and the use of paddle wheel aerators. When oxygen
depletion occurs, paddle wheels are immediately operated and, if necessary,
additional units are installed. Water exchange by overflow (10%) is also
initiated.
Transparency and color
The ideal water transparency is 30-40 cm and this is monitored by a secchi
disc. If transparency goes below 30 cm, water is changed and closely monitored
for algal collapse that is usually indicated by a change in the color of water. If
the latter occurs, 50% of the water is again changed. Algae, again, is allowed to
grow until the later stages of culture. Greenish water though ideal is difficult
to maintain, but can be done with frequent replenishment and longer paddle
wheel operation.
Temperature
A depth of 1 m ensures that pond water temperature does not fluctuate
much. Because the country is tropical, seasonal temperature fluctuation is small
though at certain months of the year (November to early March), temperature
is too cold for the shrimp (24°C). At this time, feeding is adjusted and rearing
period is extended.
pH
The pH is indicative of fertility or potential productivity. Water with pH
7.5-9.0 is suitable for shrimp. Water pH below 5.0 retards shrimp growth; it can
be raised by adding lime to neutralize acidity. Likewise, water of excessive al-
kalinity (pH 9.5) is harmful to shrimp. Ponds with abundant phytoplankton
have high pH when temperature is high and low pH when temperature is low.
Excessive plankton growth can be corrected by water change.
Predator control. Filters placed in water intake pipes or gates do not
prevent all predators from entering the ponds. Small fishes and eggs can go
through the filters and drain canals when the gates are opened during pond
39
Shrimp Grow-out Culture

6. preparation. Predators and competitors can be seen in feeding trays or along the
dikes.
Teaseed cake is the most common chemical used to eliminate fish preda-
tors. It is applied at 20-40 ppm (weight by volume) during the 45th to 50th day
of culture, coinciding with the first water exchange. Shrimp at this time weighs
5 to 10 g. Teaseed cake is applied in the morning, preferably during a sunny day
for best results. About 60% of the pond water is drained before teaseed is
applied; the required amount of powder which was dissolved in a container
overnight is broadcast around the ponds. The pond is refilled 5 h after appli-
cation.
Feeds and feeding management. Feed is the largest operational cost in
shrimp farming. Great attention should be taken to ensure efficient utilization
of feeds, enabling shrimps to attain the desired size at the targetted time frame.
It is also necessary to know the feeding habits and behavior, nutritional
requirements, and feed conversion ratio of shrimp.
Generally, traditional culture is fully dependent on natural food organ-
isms (lab-lab, lumut, phytoplankton, Najas graminae, Ruppia maritima). In semi-
intensive culture, supplemental feeds (moist/wet feed, dry pelleted feeds,
formulated pelletized feed with 40% protein) are given although natural food
organisms remain the major source of food. In intensive culture, shrimp is
completely dependent on artificial diet (Tables 3-5).
Feeding method. Feeds may be broadcast or placed in feeding trays. If
feeds are broadcast in big ponds, a dugout banca is used so that feeds can be
given in the middle of the pond. Feeding trays, on the other hand, are placed
strategically at different parts of the pond. The trays vary in size (1-10 m2
), and
they can be made of bamboo strips and polyethylene screen. Normally, there
is one tray per 10 to 100 m2
of pond area. The trays are located along the sides
(usually nine of them) and the middle (six) of the pond. The number of feed
monitoring trays depend on the size of the pond. For example:
Pond area N o . of trays
1 ha 6
l - 2 h a 8
2 - 3 h a 10
3 ha 12
During feeding, 1 % of the total amount of ration is placed in each tray. The
trays are inspected after every feeding to determine if the feeds have been
consumed. Adjustment is then made. Feeding may be adjusted after water
change, teaseed application, or when there are abnormal changes in the pond
environment. Feeding trays can also be used to determine survival rate and to
monitor health of shrimp.
Procurement of fry. One of the factors that ensure the success and
profitability of shrimp farming is the supply of good quality postlarvae (PL).
Generally, semi-intensive and intensive farming depends on hatchery bred PL
while traditional farmers get 80% of their PL from the wild.
40 Country Report: Philippines

7. Table 3. Recommended feeding rates for Penaeus monodon as percent body
weight per day
Average body
weight (g)
Feeding rate (%)
1.5 blind feeding
1.5 - 5 9.0 - 6.5
5 - 1 0 7.0 - 5.5
10 - 15 6.0 - 4.5
15 - 20 5.0 - 3 5
20 - 25 4.0 - 3.0
2 5 - 3 0 3.5 - 2.5
3 0 - 3 5 3.0 - 2.0
35 - up 2.5 - 1.5
Table 4. Recommended feeding frequencies for shrimp
Average body
weight (g)
Feeding frequency (%)
1.5 2 - 3 x
1.5 - 5 4 x
5 - 10 5 x
10 - 15 5 x
15 - 20 5 x
20 - 25 5 x
25 - 30 5 x
30 - 35 5 x
35 - up 5 x
Table 5. Recommended feed ration distribution (%) for shrimp at different feeding
frequencies and feeding schedules
Feeding
frequency
(per day)
Ration distribution (%)
Feeding
frequency
(per day)
6 am 10 am 2 pm 6 pm 10 pm 2 am
2 x 40 60
3 x 30 40 30
4 x 25 15 30 30
6 x 25 10 10 10 25 20
The various devices used to collect shrimp fry from the wild are:
1. Twig - small bunches of twigs are suspended close to or placed on the
bottom of shallow lagoons, estuaries, and coasts. The fry are collected during
low tide by placing the scoop net under each bunch of twigs as it is lifted up.
41
Shrimp Grow-out Culture

8. 2. Fry lure - 20-m lure lines are made of saltwater grass. These are usually
set along beaches and banks of rivers. Shrimp fry is collected as it is lifted up.
3. Scoop nets - in areas where aquatic weeds are abundant, a scoop net
can be used to collect shrimp fry that cling to the weeds.
4. Push or scissor nets - the nets, with or without cod ends, are used along
beaches, lagoons, bays near shore, and estuaries. They are operated by hand or
boat.
5. Fry trap - this stationary gear consists of a wing and a collecting
chamber. The cod end of the collecting chamber is kept afloat by bamboo raft
and the wing is fixed with bamboo poles against the incoming water.
6. Sagnet or bayakos - this stationary gear consists of a wing and a cod end
with a non-return valve. It is usually 20-30 m long.
The shrimp hatchery has become an important source of fry. The
advantages of hatchery-bred fry are size uniformity and its availability in bulk.
Although wild fry are good for stocking, its supply is inconsistent.
Nursery operations. Generally, shrimp farmers prefer direct delivery of
hatchery-bred PL to the farm. In intensive culture, PL are generally stocked
directly to grow-out ponds. In traditional (and some intensive) ponds, they are
stocked first in nursery ponds or cages and then transferred to grow-out ponds
after 45 days.
Nursery pond
The size of nursery pond ranges from 500 to 2,000 m2 with water depth of
40-70 cm. Ponds are prepared prior to stocking using standard pond prepara-
tion techniques, and stocked with 50-150 fry per m3 depending on size of fry.
Nursery cages
Synthetic cages (0.3 m3, 0.5-1 mm net mesh) supported by bamboo or
wooden frames are installed. Inverted mosquito nets or hapa nets may also be
used. The cages are kept afloat by raft or synthetic floats and set in rivers,
lagoons, or within the pond itself. They are usually stocked with 1,000-2,000
fry per m3 of water. Feeding screens similar to that used in ponds are also
installed in the cages.
Stocking of fry
Shrimp fry are very sensitive to abrupt changes in temperature and
salinity. They should be acclimated to pond conditions before being released by
gradually mixing the container water with pond water. The container is kept
afloat in the pond until water temperature has stabilized, and fry can be slowly
released. Optimum stocking density depends on size, natural mortality, pond
productivity, and culture system employed. The fry are best stocked during the
coldest part of the day, i.e., early in the morning (0700 - 1000 H), late in the
evening (2100 - 2400 H), or when there is incoming tide.
Problems
Several environmental and technical problems result from intensivecul-
ture system.
42 Country Report: Philippines

9. Environmental problems. Less than one-third (110,000 ha) of the original
mangroves are left in the country. Many important shrimps, fishes, and
molluscs feed and seek shelter in the mangrove ecosystem. Deforestation as a
result of mangrove conversion into ponds causes the gradual loss of critical
habitats, lowering catch in natural fishing grounds including fry and brood-
stock needed for aquaculture. A wide array of economic goods and services
including materials for fuel and construction as well as fish and shoreline
erosion control is no longer available to coastal communities.
In the 1980s, red tide predominated in some coastal areas in the country
and adversely affected the mariculture industry. Demand of fishes and mol-
luscs declined due to cases of paralytic shellfish poisoning.
Accelerated development of shrimp farms in many areas of the country,
particularly in Negros Island, led to excessive extraction of ground water. Most
intensive ponds mixed the freshwater with seawater to provide good quality
water to cultured shrimps. As a result of this excess, the water table lowered,
seawater intruded in domestic ground wells, the supply of ground water
declined, and land subsided in some areas.
Site selection. The common problems of shrimp farmers regarding site
selection are water supply, acid sulfate soils, typhoons and floods, and limited
area for expansion. Brackishwater ponds traditionally use tidal fluctuation to
supply water in higher areas. Areas reached only by extreme springtides are
costly to develop. Low areas, on the other hand, will require formidable dikes.
Aside from the tide, shrimp farms in many areas of the country require large
volume of clean freshwater. In intensive shrimp farms, freshwater is important
especially during a long dry season when salinity becomes very high due to
rapid evaporation.
Acid sulfate soils are mostly found in ponds developed along dense
mangrove vegetation. This is a problem especially during the first few years of
operation. Acid sulfate results from the accumulation of pyrites (iron sulfides)
in coastal soil. Since breakdown of pyrites is minimal in submerged soil, ponds
often have low productivity and mass kills sometimes occur.
Typhoons and floods are common problems faced by farmers in northern
Philippines. Most shrimp farms are in the flood plains and some are con-
structed within the typhoon belt especially farms in the Pacific side. Frequently
flooded shrimp farms bring risk to life and property. Often, this is a result of
poor planning and environmental impact assessment. This problem can be
minimized with proper site selection.
Shrimp farmers are unable to expand their farms because of government
regulation prohibiting conversion of mangrove areas to fishponds. Some areas,
however, have underutilized ponds which can be developed.
Design and construction. Most of the existing shrimp farms in the country
are converted from milkfish farms. It is difficult to adopt more recent innova-
tions of pond lay out such as those used in Taiwan or other countries due to the
high cost of development. Farmlands in Negros (central Philippines) that were
converted to shrimp farms (10 ha or more) are difficult to manage. Only a few
shrimp ponds continue to operate.
Despite the proliferation of engineering firms, several mistakes are still
43
Shrimp Grow-out Culture

10. being committed in pond design. Proper drainage and strict separation of
supply and drainage canals are still not given adequate consideration. Also,
most fishfarms have their gates built close to the river without provision for
strong water current and eventual sedimentation.
Pests and diseases. Intensification faces serious disease and parasite
problems because ponds usually create conditions conducive to disease out-
breaks. Once an outbreak occurs, treatment maybe too expensive for large-scale
application. In shrimp, common diseases are caused by virus, bacteria, fungi,
and protozoa. Some are caused by chemical agents.
Others. Some farmers claim that financing is a major constraint in shrimp
intensification. Site development, equipment, and other support facilities
require major capital investment. Capital is also needed particularly for the
purchase of supplemental feeds which comprise about 50-60% of the opera-
tional cost. When a lot of capital is involved, the problem is compounded
because financing assistance requires high collateral and high interest rate.
Government development banks require collaterals and the banking institu-
tions do not grant loans to fish pond lease agreement (FLA) land holders.
Shrimp growers also complain of high cost of inputs, like fertilizers, pesticides,
chemicals, and feeds which increase more rapidly than the market price of
produce.
There are also social problems affecting the shrimp industry. One is the
monopoly by big businessmen who often have joint ventures with foreign
investors. The difficulty of FLA holders to secure loans breeds discontent.
Another is displacement of labor as the daily subsistence of small-scale fisher-
men and some agricultural workers is endangered by intensification. Since
intensive shrimp ponds depend on hatchery-bred fry, only a few benefit from
employment. In traditional and extensive farms, many fry gatherers are bene-
fitted. Furthermore, a number of sugarland and overland workers or farmers
are being displaced, since the conversion of agricultural lands for shrimp
culture now requires only three maintenance workers for every 5 ha in contrast
to sugarland farms that need 8-10 laborers.
44 Country Report: Philippines

11. REFERENCES
Abesamis, G. Jr. 1989. Philippine shrimp grow-out practices. p. 98-101. In: Akiyama
(ed.). Proceedings of the Southeast Asian Shrimp Farmer Management Work-
shop; July 26-Aug. 11; Indonesia and Thailand.
Abesamis, S. and N.R. Rabanal. 1987. The shrimp industry in Luzon, Philippines. In:
Compilation of Conference Papers. Vol. 111. National Conference on Fishery
Policy and Planning; 16-20 Mar.; Baguio City, Philippines.
Apud, F.D. 1989. Recent development in prawn pond culture. p. 39-65. SEAFDEC
Aquaculture Extension Pamphlet No. 1.
Camacho, A.S. and T. Bagarinao. 1986. Impact of fishpond development on the man-
grove ecosystem in the Philippines. In: Mangroves of Asia and the Pacific: status
and management. Tech. Rep. UNDP/UNESCO Research and Training Pilot
Programme on Mangrove Ecosystems in Asia and the Pacific (RAS/79/002).
Cruz, P.S. 1991. Shrimp feeding management: principles and practices. Davao City:
Kabukiran Enterprises, Inc. p. 2-19.
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Shrimp Grow-out Culture